Long-term timolol and epinephrine in monkeys. I. Functional morphology of the ciliary processes.

Cynomolgus monkeys were treated twice daily in one eye with timolol 180 micrograms for 2.7, 6.0, or 7.4 months (2 monkeys for each period) or epinephrine 540-600 micrograms for 6.7 months (2 monkeys). Some ciliary processes in both eyes of all timolol-treated monkeys exhibited light and electron microscopic changes consistent with decreased secretion: narrowed stromal vessels with few fenestrations surrounded by a thickened fibre sheath; thickened PE basement membrane; few PE and NPE basolateral infoldings; flattened NPE with small mitochondria. Additionally, the NPE contained pigment granules and large phagolysosomes. The processes in both eyes of the epinephrine-treated monkeys exhibited one of two pictures: dilated stromal capillaries with numerous fenestrations; normal stroma, PE basement membrane and PE; numerous well-developed NPE basolateral infoldings and enlarged mitochondria; dilated stromal capillaries with ruptured fenestrations; ballooned protein-filled stroma; degenerated NPE. The first picture could be consistent with hypersecretion, the second with hyposecretion. Possible pathophysiological explanations and implications of these findings are discussed.